Lamp unit and projector employing same

ABSTRACT

A projector includes a light source, a pump which supplies a compressed gas to cool the light source, and an ejector member having a hole, in which, a tube connects the pump to the ejector member, the compressed gas is discharged from the hole, and a diameter of the hole is in a range from 0.2 mm to 0.4 mm.

The present application is a Continuation Application of U.S. patentapplication Ser. No. 12/083,313, filed on May 12, 2008 now U.S. Pat. No.7,775,689 , based on International Application PCT/JP2006/068317 filedon Sep. 13, 2007, which is based on and claims priority from Japanesepatent application No. 2006-275086, filed on Oct. 6, 2006, the entirecontents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a lamp unit including a coolingmechanism.

BACKGROUND ART

Generally, projectors include a cooling device for cooling an installedlamp. A fan is widely used as the cooling device.

JP-A No. 2003-215706 discloses a lamp unit including a reflector with alamp located at its focal point and a holder for holding the open end ofthe reflector. The open end of the reflector is covered with atransparent plate for preventing fragments from being scattered aroundin the event that the lamp blows up.

The holder has an inlet port for introducing air into the reflector andan outlet port for discharging air from the reflector. When cooling airfrom a fan disposed outside of the reflector is introduced from theinlet port into the reflector and air in the reflector is dischargedfrom the outlet port, an air flow (cooling air flow) is developed in thereflector, and impinges upon the lamp to cool the lamp.

DISCLOSURE OF THE INVENTION

However, it is difficult to obtain a sufficient cooling capability onlywhen the air flow (cooling air flow) produced by introducing the coolingair from the fan into the reflector impinges upon the lamp.

High-pressure mercury lamps that are widely used with projectors have aheated region that should desirably be cooled locally. It is difficultto perform such local cooling with a fan.

It is an exemplary object of the present invention to provide a lampunit which will solve the above problems and which is capable ofapplying cooling air at a sufficient speed highly accurately to adesired region of a lamp.

To achieve the above object, a lamp unit according to an exemplaryaspect of the present invention comprising a reflector with a lampmounted therein, by which light from the lamp is reflected, a reflectorholder that holds the reflector, and an ejector member fixed to thereflector holder, which ejects air to cool the lamp. The ejector memberincludes an insertion member to which a tubular air supply member thatsupplies compressed air to the ejector member is inserted, a fluidpassage forming member that includes a fluid passage to which air issupplied from a distal end of the air supply member inserted in theinsertion member, and at least one small hole defined in a distal end ofthe ejector member and that extends through a fluid passage walldefining the fluid passage. The fluid passage forming member includes afluid passage cross-sectional area which is smaller at the distal end ofthe ejector member than at the insertion member.

According to the present invention as described above, compressed airfrom a pressurized is supplied through the air supply member to theejector member which discharges the cooling air through the small holedefined in the distal end thereof. The cooling air discharged from thesmall hole is applied to the lamp unit to cool the lamp locally.

In the present invention, furthermore, the reflector with the lampmounted therein is held by the reflector holder, and the ejector memberis fixed to the reflector holder. Thus, both the lamp and the ejectormember are positioned with respect to the reflector holder. Since thesame member is used as a reference for positioning the lamp and theejector member, the positional relationship between the lamp and theejector member is set with high accuracy, with the result that thecooling air discharged from the small hole of the ejector member can beapplied highly accurately to a desired area of the lamp.

If the lamp and the ejector member are positioned with respect todifferent reference members, then as the positioning accuracy with whichthe reference members position the lamp and the ejector member and thepositioning accuracy between the reference members need to be taken intoaccount, it is difficult to set the positional relationship between thelamp and the ejector member highly accurately.

According to the present invention, the air supply member is inserted inthe ejector member to realize an exchangeable unit structure. In such astructure, the size of the cross section of the fluid passage at theinsertion member is greater than the outer profile of the air supplymember. If the fluid passage cross-sectional area is the same as thefluid passage cross-sectional area at the insertion member throughoutthe fluid passage forming member, then the compressed air supplied fromthe air supply member is introduced into the fluid passage as a largespace, whereupon the air suffers a pressure loss, resulting in areduction in the speed of the air discharged from the small hole. Thefluid passage cross-sectional area of the fluid passage forming membercan be reduced to minimize a reduction, caused by the pressure loss, inthe speed of the air discharged from the small hole. According to thepresent invention, since the fluid passage cross-sectional area at thedistal end of the ejector member is smaller than the fluid passagecross-sectional area at the insertion member, the speed of the airdischarged from the small hole is increased.

According to the present invention, as described above, inasmuch as thecooling air is discharged at a sufficient speed from the small hole ofthe ejector member, and the cooling air is applied highly accurately toa desired area of the lamp (high-pressure mercury lamp or the like), thelamp can be maintained at an appropriate temperature. Therefore, thelamp is prevented from becoming clouded and blackened (due to mercurydeposition or anode spot on the inner wall surface of the lamp), and, asa consequence, has a longer service life and is of higher reliabilitythan heretofore.

The above and other objects, features, and advantages of the presentinvention will become apparent from the following description withreference to the accompanying drawings which illustrate examples of thepresent invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a lamp unit according to an exemplaryembodiment of the present invention;

FIG. 2 is an exploded perspective view of a nozzle assembly including anejector member shown in FIG. 1;

FIG. 3 is a cross-sectional view of an example of the ejector membershown in FIG. 1;

FIG. 4 is a cross-sectional view of another example of the ejectormember shown in FIG. 1;

FIG. 5 is a characteristic diagram showing the relationship between thediameter of a small hole and the air speed;

FIG. 6 is a view showing the positional relationship between the ejectormember and a lamp (light emission tube);

FIG. 7 is a view showing the positional relationship between the ejectormember and the lamp (light emission tube);

FIG. 8 is a perspective view of a major portion of a projector whichincorporates the lamp unit shown in FIG. 1; and

FIG. 9 is an exploded perspective view of some of the major portion ofthe projector shown in FIG. 8.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a perspective view of a lamp unit according to an exemplaryembodiment of the present invention. As shown in FIG. 1, the lamp unit,which is to be incorporated in a projector, comprises reflector 10including a lamp and reflector holder 20 holding the open end ofreflector 10. Reflector 10 has a concave reflecting surface, e.g., areflecting surface as a paraboloid of revolution, with the lamp locatedat the focal point thereof. Light from the lamp is emitted directly fromthe opening or reflected by the reflecting surface and then emitted fromthe opening in a certain direction.

Reflector holder 20 is in the form of a cup covering the open end ofreflector 10, and has circular window 21 for passing therethrough thelight emitted from the open end of reflector 10. Window 20 is made of atransparent material (such as glass or resin) having such propertiesthat it passes therethrough light in a wavelength range used in thedevice which incorporates the lamp unit.

Reflector holder 20 includes attachment 27 on which ejector member 22 ismounted, positioning members 24 through 26 by which reflector holder 20is positioned on an engine base, inlet duct 29 for introducing air froma fan, not shown, into the reflector, and outlet port 100 fordischarging air from the reflector. Positioning members 24 through 26are in the form of pins for engaging in receptacles (holes or the like)in certain locations on an external member. Reflector holder 20 may havefour or more positioning members. Reflector holder 20 are positioned bypositioning members 24 through 26 and then fastened to the engine basesby screws. In addition to the lamp unit, optical components of anilluminating optical system, a projection lens, and an image displaydevice (DMD) are mounted on the engine base.

FIG. 2 is an exploded perspective view of a nozzle assembly includingejector member 22. As shown in FIG. 2, ejector member 22 is tubular andhas small hole 221 for ejecting air which is defined therein near thedistal end thereof. Ejector member 22 has an open end remote from thedistal end thereof. Connector 23 has stud 23 a inserted into ejectormember 22 through the open end thereof.

Connector 23 comprises an L-shaped vent pipe and has an end attached toa tube connected to the outlet port of a pressurizing pump, not shown.Tubular stud 23 a for supplying ejector member 22 with compressed air ismounted on the other end of connector 23. Stud 23 a is inserted throughpacking 28 into ejector member 22. Packing 28 serves to prevent air fromleaking from the junction between packing 23 a and ejector member 22,and is made of silicone, for example. Packing 28 may be fixed to theopen end of ejector member 22 by an adhesive, and stud 23 a mayremovably be fixed in position by fixed packing 28.

The open end of ejector member 22 has holes 222, 223 through whichejector member 22 is fastened to attachment 27 of reflector holder 20.Attachment 27 has an opening through which ejector member 22 isinserted, and also has pin 271 and screw hole 272 near the opening. Pin271 is inserted in hole 222 of ejector member 22, and ejector member 22is positioned to keep hole 223 immediately above screw hole 272. Ascrew, not shown, is then inserted through hole 223 into screw hole 272,fastening ejector member 22 to attachment 27 of reflector holder 20.With ejector 22 fastened to reflector holder 20, compressed airdischarged from small hole 221 impinges upon a desired area of the lampin reflector 10.

FIG. 3 is a cross-sectional view of an example of ejector member 22. Asshown in FIG. 3, ejector member 22 comprises tube 22 a into which stud23 a is inserted and tube 22 b which is smaller in side diameter thantube 22 a. Tubes 22 a, 22 b have respective centers “a” substantiallyaligned with each other on a sectional plane transverse to thelongitudinal direction of these tubes. Small hole 221 is defined in theside wall of tube 22 b. The side wall of tube 22 b has a thickness whichshould preferably about three times the diameter of small hole 221. Forexample, if the diameter of small hole 221 is 0.3 mm, then the thicknessof the side wall of tube 22 b is 1.0 mm.

As stud 23 a is inserted in ejector member 22, the inside diameter oftube 22 a is greater than the outer profile of stud 23 a. If the insidediameters of tubes 22 a, 22 b are essentially the same as each other,then the inside diameter of the entire tube assembly is greater than theouter profile of stud 23 a. In other words, the cross-sectional area ofthe fluid passage in ejector member 22 is greater than thecross-sectional area of the fluid passage in stud 23 a. In this case,compressed air discharged from stud 23 a is introduced into the fluidpassage as a large space and thereafter ejected out of ejector member 22through small hole 221. When the compressed air discharged from stud 23a is introduced into the fluid passage as a large space, the air suffersa pressure loss, resulting in a reduction in the speed of the airdischarged from small hole 221.

The difference between the cross-sectional area of the fluid passage inejector member 22 and the cross-sectional area of the fluid passage instud 23 a is reduced to minimize a reduction, caused by the pressureloss, in the speed of the air discharged from small hole 221.Specifically, the cross-sectional area of the fluid passage in ejectormember 22 which leads to small hole 221 is reduced stepwise (orcontinuously) from the side where the stud is inserted, thereby loweringa pressure loss and increasing the speed of the air discharged fromsmall hole 221. With the structure shown in FIG. 3, since the insidediameter of tube 22 b is smaller than the inside diameter of tube 22 a,the cross-sectional area of the fluid passage in ejector member 22 isreduced as much, for thereby increasing the speed of the air dischargedfrom small hole 221.

FIG. 4 is a cross-sectional view of another example of ejector member22. As shown in FIG. 4, ejector member 22 comprises tube 22 a into whichstud 23 a is inserted and tube 22 c which is smaller in side diameterthan tube 22 a. Tubes 22 a, 22 c have respective centers displaced fromeach other in a sectional plane transverse to the longitudinal directionof these tubes. Specifically, ejector member 22 is of an eccentricstructure wherein the center “b” of tube 22 c is displaced from thecenter “a” of tube 22 a toward the side where small hole 221 is defined.

In the ejector member shown in FIG. 3, a step is present in the boundarybetween tube 22 a and tube 22 b on the side where small hole 221 isdefined, and the outlet port of small hole 221 is spaced from the lampby the step. The speed of the compressed air discharged from small hole221 is lower as it is spaced greater from the outlet port. According tothe eccentric structure shown in FIG. 4, there is no step in theboundary between tube 22 a and tube 22 c on the side where small hole221 is defined. In the absence of the step, outlet port of small hole221 is positioned more closely to the lamp, so that the speed of thecompressed air for cooling the lamp can be higher than with thestructure shown in FIG. 3.

The speed of the compressed air discharged from small hole 221 variesdepending on the diameter of small hole 221. FIG. 5 shows therelationship between the diameter of the small hole and the air speed.The graph shown in FIG. 5 indicates the results of an experiment inwhich the relationship between the diameter of the small hole and theair speed was measured when constant compressed air was introduced. Theresults show that if the diameter of small hole 221 is smaller than 0.2mm, then the value of the air speed drops sharply because of increasedresistance to the compressed air as it passes through small hole 221,and if the diameter of small hole 221 is in excess of 0.4 mm, then thevalue of the air speed becomes lower than 20 m/s. As at least the airspeed of about 20 m/s is required for locally cooling the lamp used inthe projector, the diameter of small hole 221 should preferably be inthe range from 0.2 mm to 0.4 mm. More preferably, the diameter of smallhole 221 should be in the range from 0.2 mm to 0.3 mm. With thisdiameter range, the air speed is equal to or higher than 30 m/s.

The positional relationship between ejector member 22 and the lamp(light emission tube) will be described in specific detail below.

FIGS. 6 and 7 are views showing the positional relationship betweenejector member 22 and the lamp (light emission tube). FIG. 6 illustratesthe lamp unit shown in FIG. 1, with reflector holder 20 omitted fromillustration, and FIG. 7 illustrates the lamp unit shown in FIG. 6,showing the small hole and parts near the light emission tube as viewedfrom above.

As shown in FIGS. 6 and 7, ejector member 22 is disposed at such anangle that the compressed air discharged from small hole 221 impingesupon a desired area of light emission tube 30 disposed in reflector 10,and in such a position that ejector member 22 does not block lightfluxes emitted from reflector 10 and passing through window 21 (lightfluxes in an effective range). In FIGS. 6 and 7, the arrow A representsthe direction in which the compressed air is discharged from small hole221.

If the ejector member and the reflector holder are of an integralstructure, then it is difficult to form the small hole to a nicety. Withthe lamp unit according to the present embodiment, since ejector member22 is separate from reflector holder 20, small hole 221 can be machinedwith high accuracy. The positioning means (holes 222, 223, pin 271)shown in FIG. 2 allows the ejector member to be mounted highlyaccurately on the reflector holder. As the highly accurate machiningprocess and the highly accurate positioning process are realized, it ispossible to apply the compressed air from small hole 221 exactly to adesired area of the lamp. The stepped structure shown in FIG. 3 and theeccentric structure shown in FIG. 4 are effective to apply thecompressed air from small hole 221 at a higher speed to a desired areaof the lamp. Consequently, the desired area of the lamp can bemaintained at an appropriate temperature, with the results that the lampis prevented from becoming clouded and blackened (due to mercurydeposition or anode spot on the inner wall surface of the lamp), has along service life, and is of increased reliability.

A projector incorporating the lamp unit according to the presentexemplary embodiment will be described in specific detail below.

FIG. 8 is a perspective view of a major portion of a projector whichincorporates the lamp unit shown in FIG. 1. FIG. 9 is an explodedperspective view of some of the major portion of the projector shown inFIG. 8.

As shown in FIG. 8, the major portion of the projector comprises lampunit 1, engine base 2, fan 3, and diaphragm-type air blower 4. Lamp unit1, which is the lamp unit shown in FIG. 1, is accurately positioned onengine base 2 by positioning members 24 through 26 and fastened toengine base 2.

Diaphragm-type air blower 4 comprises an existing pressurizing pump andhas an outlet port connected to connector 23 through silicone tube 5.Compressed air discharged from diaphragm-type air blower 4 flowssuccessively through silicone tube 5, connector 23, and stud 23 a intoejector member 22, from which the compressed air is discharged throughsmall hole 221 toward the lamp. Fan 3 draws air from fan duct 3 a. Anair stream delivered by fan 3 is introduced through an inlet duct 29into reflector 10.

On engine base 2, there are mounted an illuminating optical system towhich light fluxes (parallel light fluxes) emitted from window 21 oflamp unit 1 are applied, and a spatial modulator device for beingirradiated with the light fluxes from the illuminating optical system.The spatial modulator device comprises, for example, a liquid crystalpanel or DMD (Digital Micromirror Device), for example. Image light thatis generated by the spatial modulator device is projected onto anexternal screen by a projection optical system, not shown.

The projector is cooled by both diaphragm-type air blower 4 and fan 3.Specifically, diaphragm-type air blower 4 can locally cool a heatedregion of the lamp, and fan 3 can cool the lamp in its entirety. Thelocal cooling provided by diaphragm-type air blower 4 makes it possibleto perform accurate temperature management of various parts of the lamp,which has not been achieved by the cooling provided by the fan alone,for increasing the service life of the lamp.

In the lamp unit according to the present invention, the compressed airfrom the pressurizing pump is supplied through the stud, which serves asan air supply member, to the ejector member which discharges the coolingair through the small hole defined in the distal end thereof. Thecooling air discharged from the small hole is applied to the lamp unitto cool the lamp locally.

In the lamp unit according to the present invention, furthermore, thereflector with the lamp mounted therein is held by the reflector holder,and the ejector member is fixed to the reflector holder. Thus, both thelamp and the ejector member are positioned with respect to the reflectorholder. Since the same member is used as a reference for positioning thelamp and the ejector member, the positional relationship between thelamp and the ejector member is set with high accuracy, with the resultthat the cooling air discharged from the small hole of the ejectormember can be applied highly accurately to a desired area of the lamp.

In the lamp unit according to the present invention, as shown in FIGS. 3and 4, the cross-sectional area of the fluid passage which leads to thesmall hole is reduced stepwise or continuously toward the distal end ofthe ejector member. Consequently, a reduction, caused by a pressureloss, in the speed of the air discharged from the small hole isminimized.

According to the present invention, as described above, inasmuch as thecooling air is discharged at a sufficient speed from the small hole ofthe ejector member, and the cooling air is applied highly accurately toa desired area of the lamp (high-pressure mercury lamp or the like), thelamp can be maintained at an appropriate temperature. Therefore, thelamp is prevented from becoming clouded and blackened (due to mercurydeposition or anode spot on the inner wall surface of the lamp), and, asa consequence, has a longer service life and is of higher reliabilitythan heretofore.

The lamp unit which has been described above is an example of thepresent invention, and can be changed in structure without departingfrom the scope of the invention. For example, ejector member 22 may beof any structures insofar as the cross-sectional area of the fluidpassage of ejector member 22 can be reduced. For example, ejector member22 may be of a tapered structure in which the cross-sectional area ofthe ejector member is gradually smaller from the side wherein stud 23 ais inserted.

The small hole 221 defined in the distal end of ejector member 22 is notlimited to a single small hole. Instead, a plurality of small holes 221may be defined in the distal end of ejector member 22 for simultaneouslycooling a plurality of areas of the lamp with cooling air from the smallholes.

Small hole 221 may be defined in the surface of the distal end ofejector member 22 (specifically, the wall at the end of the fluidpassage in tube 22 b.

A plurality of ejector members 22 may be provided on reflector holder 20for simultaneously cooling a plurality of areas of the lamp with coolingair from the ejector members.

The lamp unit according to the present invention is applicable toprojectors in general. The lamp unit according to the present inventionis also applicable to display devices for use with personal computers,e.g., liquid crystal display devices, in addition to projectors.

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2006-275086 filed in Japan Patent Officeon Oct. 6, 2006, the contents of which are hereby incorporated byreference.

While preferred embodiments of the present invention have been describedusing specific terms, such description is for illustrates purposes only,and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

1. A projector, comprising: a light source; a pump which supplies acompressed gas to cool said light source; and an ejector member having ahole, wherein a tube connects said pump to said ejector member, saidcompressed gas being discharged from said hole, and wherein a diameterof said hole is in a range from 0.2 mm to 0.4 mm.
 2. The projectoraccording to claim 1, wherein said pump comprises a pressurizing pump.3. The projector according to claim 1, wherein said pump comprises adiaphragm-type air blower.
 4. The projector according to claim 1,further comprising a cooling fan which supplies cooling air to theprojector.
 5. The projector according to claim 4, wherein said lightsource is cooled by both said compressed gas and said cooling air. 6.The projector according to claim 1, wherein said hole is placed in asidewall of a tube of said ejector member.
 7. The projector according toclaim 6, wherein the sidewall of the tube of said ejector member has athickness of about three times the diameter of said hole.
 8. Theprojector according to claim 1, wherein a cross-sectional area of afluid passage in the ejector member which leads to the hole is reducedtoward a distal end of the ejector member.
 9. The projector according toclaim 1, wherein said ejector member comprises one of a plurality ofejector members provided in the projector to provide said compressed gasto multiple areas in the projector.
 10. The projector according to claim1, wherein said ejector member comprises: an insertion member to whichthe tube is inserted; and a fluid passage forming member having a fluidpassage to which the compressed gas is supplied from the tube insertedin said insertion member.
 11. The projector according to claim 10,wherein said hole is placed in a distal end of said ejector member andextends through a fluid passage wall defining said fluid passage. 12.The projector according to claim 10, wherein said fluid passage formingmember has a fluid passage cross-sectional area which is smaller at adistal end of said ejector member than at said insertion member.
 13. Theprojector according to claim 10, wherein said fluid passage formingmember comprises: a first fluid passage forming member; and a secondfluid passage forming member that has a fluid passage cross-sectionalarea smaller than that of said first fluid passage forming member, saidhole being placed in said second fluid passage forming member.
 14. Aprojector, comprising: a light source; a pump which supplies acompressed gas to cool said light source; and an ejector member fordischarging said compressed gas, said ejector member comprising: aninsertion member to which a tube that connects said pump to said ejectormember is inserted; a fluid passage forming member having a fluidpassage to which the compressed gas is supplied from the tube insertedin said insertion member; and a hole placed in a distal end of saidejector member, said hole extending through a sidewall of said fluidpassage.
 15. The projector according to claim 14, wherein a diameter ofsaid hole is in a range from 0.2 mm to 0.4 mm.
 16. The projectoraccording to claim 14, wherein said fluid passage forming member has afluid passage cross-sectional area which is smaller at the distal end ofsaid ejector member than at said insertion member.
 17. The projectoraccording to claim 14, wherein the sidewall of the tube of said ejectormember has a thickness of about three times the diameter of said hole.18. The projector according to claim 14, wherein a cross-sectional areaof the fluid passage in the ejector member which leads to the hole isreduced toward the distal end of the ejector member.